1. Field of the Invention
This invention relates to a polyimide composition, a prepreg formed with the polyimide composition and a polyimide laminate formed with the prepregs laminated and set.
The polyimide laminate of the kind referred to is effectively utilizable in manufacturing printed-wiring boards, in particular, highly multilayered wiring substrate and so on for high-density mounting use.
2. Description of the Related Art
The polyimide laminate has been increasingly utilized in recent years in manufacturing the multilayered wiring substrate, because of such characteristics that polyimide allows wiring conductor to be finely dimensioned and such high precision work as fine perforation and the like made possible for adaption of the wiring substrate to the high-density mounting, that the polyimide laminate shows only a small thermal expansion coefficient in the direction of thickness in laminated state of the prepregs and is thus high in the reliability of electric conduction attainable by means of through-hole metal plating, that polyimide involves no smear generation during drilling step, that high hardness and adhesion with respect to conducting member at higher temperatures render the mountability excellent, that the laminate is durable in consecutive use under such high temperatures as around 200.degree. C., and so on. The multilayered wiring substrate employing polyimide has been disclosed in, for example, Japanese Patent Application Laid-Open Publication No. 59-20659 or 61-40322.
It has been generally demanded, on the other hand, that the multilayered wiring substrate is effectively lowered in the dielectric constant to allow a high speed signal propogation to be enabled, and a measure for providing a substrate of the kind referred to which is higher reliable in the through-hole conduction and low in dielectric constant has been disclosed in, for example, U.S. Pat. application Ser. No. 165,011.
Such known composition as well as the multilayered wiring substrate formed by the composition as has been referred to are, however, still defective in attaining sufficiently highly reliable conduction for being fully satisfactory particularly in respect of the through-hole plating made in the substrate, and this deficiency is required to be removed for realizing the wiring substrate adapted to the high-density mounting.